Thermally expanded core fibers with nanoprinted periodic structures for improved light collection at large angles of incidence

Efficient light collection is critical in many scientific and technological fields. We have shown that the integration of nanoprinted structures with thermally expanded core (TEC) fibers enhances light coupling at large angles of incidence while maintaining single-mode operation due to the increased mode field diameter at the fiber tip. Large-area ring gratings have been fabricated on TEC-fibers using 3D nanoprinting, and their performance has been validated by both experiment and simulation. This approach holds promise for applications such as single-photon collection, in vivo imaging, and optical coherence tomography, and paves the way for compact, multifunctional photonic devices.